The Blue Revolution:
The Key to Hydrogen from OTEC
Patrick TAKAHASHI, Stephen MASUTANI and Kenji SUMIDAUniversity of Hawaii
1680 East-West Road, POST 109, Honolulu, HI 96822
While the Green Revolution improved grain cultivation and has been recognized as an important accomplishment of science, the Blue Revolution promises much more. All indications are that the Next Frontier is not space, but the open ocean. At 1000 meter depths in the region bounded by the Tropics of Cancer and Capricorn, is nutrient-rich seawater at 4°C, that can serve as a cold thermal sink for ocean thermal energy conversion (OTEC) systems to produce electricity, and as fertilizer to sustain mariculture activities. If only one part in ten thousand of the daily insolation falling in this band can be converted to useful products, the food and energy needs of society would be satisfied in-to the foreseeable future. This warm portion of the ocean is characterized as a wet desert, for the net primary productivity is low at around one-tenth that of tropical rain forests. However, as cer-tain aquatic species are known to be from two to five times more efficient than any terrestrial plant, if technology can be developed to utilize this currently unused resource base, at hand will be a vast region providing immense sustainable resource and habitat opportunities. The Blue Revolution promises this broad package of natural products, only one possible option being hydrogen fuel.
hydrogen production, ocean thermal energy conversion, Blue Revolution
While Henry Cavendish discovered hydrogen in 1766, the early history of OTEC begins with D’Arsonval, of France, who first proposed the con-cept in 1881. One of his students, Georges Claude, conducted field experiments off Cuba in the 1930’s. As has been the experience with many ocean engi-neering demonstrations, a major storm damaged the equipment and Claude never was able to attain net positive electricity.
The modern history has mostly taken place in Hawaii, with a sprinkling of Japanese projects, al-though India now appears ready to join the net-positive club. Mini-OTEC, a venture headed by Lockheed, reached a net output of 18 kW on a gov-ernment barge off Keahole Point of the Big Island of Hawaii in 1979. It is interesting to note that in the months following, Senator Spark Matsunaga introduced the very first OTEC and hydrogen bills in the U.S. Senate. OTEC legislation was enacted
1980, and went so far as mentioning a 1999 target of 20,000 MW, but it took another decade for the hydrogen bill to be passed by Congress and signed and named the Matsunaga Act by then-President George H.W. Bush in 1990. Both concepts, though, remain in the formative stage. Unless the India experiment succeeds, OTEC will stay at zero MW installed capacity, and hydrogen continues to be a very expensive proposition.
The Natural Energy Laboratory of Hawaii Au-thority on the West Coast of the Big Island of Ha-waii (see Figure 1) has been home to the major OTEC projects and sprouting marine nutraceuti-cals, coldwater agriculture crops, seafood, pearls, and a range of other products. Nearing a quarter century of operation, about 30 companies are pro-ducing a variety of bioproducts using deep ocean water. Japan now has more than ten such facilities, but mostly for special shrimp, vegetable and imbib-able commodities. Korea and other countries of Asia are planning similar activities.
The Blue Revolution came together through a se-ries of workshops and conferences in the United States [1,2,3] as a natural outgrowth of the early OTEC experiments, for it became immediately clear that OTEC electricity would be very expen-sive for a long time to come, but that the nutrient-rich, coldwater effluent had special attractive quali-ties to make the package of co-products commer-cially interesting. A recent thrust appears to be the possibility of the United Nations taking on the mission to coordinate international cooperation in this area [4]
OCEAN THERMAL ENERGY CONVERSION (OTEC)
The driving natural mechanism to power the Blue Revolution is ocean thermal energy conver-sion, or OTEC, a proven, well-documented
technol-ogy that extracts clean, renewable solar thermal energy from temperature differences in the ocean [5,6,7]. The U.S. Federal government alone has spent more than $250 million on OTEC R&D. Ja-pan, India, France and Taiwan have also expended many tens of millions.
There are three primary production cycles: open, closed and hybrid. Open cycle generally can be con-figured to produce the most amount of freshwater, and all show, because of attractive deep ocean wa-ter properties, huge potential for supporting a range of co-products, from aquaculture to air condi-tioning to environmental remediation.
References 5-7 can be consulted to learn more about the thermodynamics, technology and applica-tions areas. Suffice it to say that OTEC works in a manner just the opposite of a conventional refrige-rator that consumes electricity to cool things, while discarding heat. For OTEC, the temperature dif-Figure 1. Aerial Photo of the Natural Energy Laboratory of Hawaii Authority
ference of the warm surface and cold deep waters can be applied in a Rankine cycle to produce elec-tricity. As this delta T (about 20 Celsius degrees) is small, the efficiency is low, meaning that the hard-ware must be massive and expensive. But the fuel, ocean water, is free, and no nuclear and minimal carbon, sulfur and nitrogen gaseous waste com-pounds are emitted. However, to be perfectly cor-rect, carbon dioxide from the deep ocean water can escape to the atmosphere if marine biomass is not utilized within the total system.
The ocean regions which are best suited for OTEC are located near the equator. All the present total world energy demand, and more, can be sup-plied through conversion of the ocean water tem-perature differential that prevails in this zone, ei-ther through the generation of electricity or produc-tion of energy carriers such as hydrogen, ammonia or methanol.
The primary feature of the ocean in this locality is that the surface temperatures are more than 20 C degrees warmer than the deeper waters at 1000 meters, which the world over is in the range of 4 degrees Celsius. The second advantage of this 1000 meter fluid is that it is rich in nutrients, in the ex-act proportion as is necessary to promote growth, for these compounds derived from sea life in the photic zone. For example, comparing the water quality of surface with 600 meter waters off Kea-hole Point in Hawaii [8], there is 78 times more ni-trogen and 15 times more phosphorous in the dee-per waters.
Widespread implementation of OTEC has not occurred, primarily because of very high capital costs. However, increasing fossil fuel prices and/or possible future restrictions on the use of these con-ventional energy sources, combined with co-products, including value added environmental benefits, make OTEC a serious contender for future application. Project Blue Revolution was formed to provide a systems approach to integrating all ele-ments of the endeavor.
OTEC TECHNOLOGY DEVELOPMENT
The three critical OTEC components needing breakthroughs are the closed and hybrid cycle heat exchanger, open cycle turbine and coldwater pipe. These are the major pieces of system equipment costing the most dollars.
Titanium was initially used in the heat exchang-er because the goal was to prove technical feasibili-ty, that is, show that the temperature differential in the ocean could be used to produce net positive energy. It worked. Now, the key will be cheaper materials. Aluminum appears to be the metal of choice. The economics look promising. A factor of ten improvement in cost appears to be feasible, and much of this has been shown to work in prototype experiments.
The low pressure, open cycle OTEC turbines that have been employed to date in prototype OC-OTEC systems were retro-fit orphans from industry. Open cycle systems are currently limited by a max-imum validated (tested) turbine capacity of 250 kW. At 5 megawatt and larger sizes, either an expen-sive modular approach must be adopted or innova-tive turbines need to be developed that take advan-tage of next generation non-metallic materials. There is no market today to promote this develop-ment.
A 30 meter diameter coldwater pipe will be re-quired for a 400 MW floating OTEC powerplant. Pipes for OTEC have been manufactured from plastic and/or steel. The utilization of deep ocean pumps pushing the fluid up an inflatable fabric pipe has been discussed to reduce material costs. Mooring and structural strength then will become follow-on problems. Very little R&D has gone into developing innovations.
OTEC FOR ENVIRONMENTAL REMEDIATION
The widespread use of OTEC would displace fos-sil fuel consumption and reduce atmospheric emis-sions of greenhouse gases. This would contribute to reducing radiative forcing that can negatively affect global climate. In addition, should a means be de-veloped to promote marine biomass growth using the deep ocean nutrients, it may be possible to
modestly increase carbon dioxide uptake from the atmosphere for photosynthesis [9]. It should be noted, however, that deep ocean water contains substantial amounts of carbon that can by itself sustain the photosynthetic processes that will occur when the deep water is exposed to sunlight.
The combination of a floating coal powerplant with an OTEC facility to enable deep ocean seques-tration of CO2 has been proposed [10]. OTEC uses
cold deep sea water as a thermal sink, while ocean sequestration treats it as a repository for anthropo-genic CO2. These technologies have the potential
for synergy, including the sharing of platforms and equipment, addition of CO2 to the warm water
OTEC intakes to prevent biofouling of pipelines and heat exchangers, exploiting the negatively buoyant CO2 enriched sea water to drive part of the
upward water transport for OTEC, reduction of pumping costs for sequestration, and carbon tax credits.
As an early next step, the International Ocean Alliance Floating Platform Summit [11] suggested a demonstration on a decommissioned oil platform, combining a 10-100 MW fossil fuel powerplant, small OTEC system and various associated co-products for testing offshore Hawaii waters. Hy-drogen would be one of those products. In the long term, as OTEC grazing plantships will be located in the warmest portion of the oceans, where hurri-canes are formed, it might be possible to reduce the intensity of these ocean storms with an armada of platforms as a result of the associated surface wa-ter cooling [12].
OTEC ECONOMICS
The electricity from next generation 1-10 MW OTEC facilities will cost more than $0.25/kWh. There have been island communities long in this price range, with some approaching an unsubsi-dized $1/kWh. With freshwater, aquaculture, air-conditioning and other co-products, a major resort or military base could justify the installation of an OTEC powerplant.
A 1 MW OTEC plant can produce up to 3500 cubic meters per day of potable water. The value added operational and marketing benefits of natu-ral energy and self-sustainability are exploitable advantages. While the U.S. Department of Defense has carried out several studies to consider this al-ternative, there are hopes that an international governmental funding organization will have the will to break from tradition to symbolically demon-strate the value of this sustainable option. UNES-CO of the UN has been approached to investigate.
With water credit, the Pacific International Cen-ter for High Technology Research has reported that a land-based 1 MW plant could be built to produce electricity at $0.25/kWh and 5 MW for about $0.10/kWh [13]. A 50 MW floating closed cycle hy-brid OTEC facility, with water sold at $3/1000 gal-lons ($3/3.8 m3), could produce electricity for
$0.06/kWh (1990 dollars), although cost-effective transport of the water poses a challenge.
The fact of the matter is that energy prices are artificially maintained. Controlling forces, from industry and government, enjoy and want to main-tain the current status quo. While World trends point to a greener future over time, the price of the Middle East wars and damage to the environment do not equitably enter into the cost of energy. These externalities can be accommodated through carbon taxes, elimination of certain fossil and nuc-lear incentives, carbon trading, add-ons to the price of gulf oil, and so on. OTEC/hydrogen and all the sustainable energy options, thus, will continue to have difficulty competing with the conventional alternatives unless a SARS-like or September 11 incident — like a really hot summer, where tens of millions perish — can galvanize decision-makers to level the playing field.
Short of a major crisis, then, OTEC electricity will not be commercially competitive for many years to come. With water, carbon, and/or co-product credits, the equation dramatically shifts in the direction of OTEC for niche island applications today. In the mid term, as oil becomes scarce, OTEC hydrogen and other fuels and chemicals can become attractive options depending on how much
conventional energy costs subsequently rise. In the very long term, the concept of artificial upwelling for broad scale marine development with concomi-tant environmental benefits looms large as an ex-citing future.
HYDROGEN OVERVIEW
Hydrogen has been touted as the clean fuel of the future, but substantial technical, infrastructure, and economic challenges remain to be overcome before this dream becomes reality. The energy in commercially produced hydrogen currently stands at less than 1% of the world’s energy consumption, with the vast majority of the H2 employed for
chem-ical synthesis. Moreover, most hydrogen continues to be produced from fossil fuels (e.g., steam reform-ing of natural gas) which attaches a greenhouse gas carbon penalty to H2.
It is unnecessary to provide an extensive discus-sion on the state of hydrogen development, as this is a journal on this subject. However, in tune with many of the marine related activities ongoing in Hawaii are several showcase hydrogen projects worthy of mention.
In 2003, the Hawaii Fuel Cell Test Facility began operations in downtown Honolulu. This 4,000 ft2
(370 m2) facility currently houses three test stands
designed to characterize full-size single-cell PEM fuel cells and a host of supporting equipment in-cluding on-site hydrogen generation and storage. Another project underway is the Hawaii Hydrogen Power Park. This facility will deploy and demon-strate an integrated system comprising electrolysis for hydrogen production, hydrogen storage, and a grid-connected fuel cell. The project will be located where a renewable energy source could be used for hydrogen production. Additional efforts at the University of Hawaii include research on ocean re-sources (CO2 sequestration and methane hydrates),
photoelectrochemical hydrogen production, biologi-cal hydrogen production, and hydrogen production by catalytic gasification of biomass in supercritical water.
THE BLUE REVOLUTION
The total marine system effort, beginning with exploratory science, through engineering develop-ment and field demonstrations, to develop new products and habitats in an environmentally en-hancive manner, is the Blue Revolution. Picture, then, a grazing plantship, powered by OTEC, sup-porting a marine biomass plantation with next generation ocean ranches. Figures 2 and 3 depict the marine environment and systems configuration to capture this potential. Then consider several hundred, maybe even thousands, of these produc-tive platforms. Current international law dictates that each, under certain circumstances, can legally become a nation. Imagine the United Nations in the 22nd Century.
Such is the promise and political complexity made possible by the Blue Revolution. Much of the thinking and early planning began a little more than a decade ago, when workshops were held, pa-pers were published and plans were sanctioned. This was a period just after the end of the Cold War, when the notion of dual military-civilian applica-tions was in vogue.
In 1992 the National Science Foundation and National Oceanic and Atmospheric Administration commissioned a study called “U.S. Ocean Resources 2000,” to serve as a blueprint for action [1]. An oth-er gathoth-ering linked to the Pacific Congress on Ma-rine Science and Technology in 1992 projected that a 100,000 ft2 (930 m2) ocean resource incubator
platform could be built and operated in the year 2000 for $500 million. It was argued that in view of the $2.4 billion cost of each B-2 bomber, this was an opportunity that could not be wasted. No peace dividend appeared after the fall of the Berlin Wall, and the opportunity, indeed, passed by.
What of the future? It can be projected that the Blue Revolution will occur, but maybe more slowly than earlier anticipated. Japan and Korea, the two largest shipbuilders can justify using their shi-pyards because they have very little natural re-sources and the open ocean is available at no politi-cal or financial cost. Japan, for example, has ten ti-
Figure 3. Configuration of Systems Within the Blue Revolution Mission Figure 2. Marine Environment for a Blue Revolution System
mes more space in their Exclusive Economic Zone than on land, and Okinawa is marginal, but avail-able, as an OTEC development site.
European seafaring nations might again consider colonization, this time the open ocean, where there are no obvious downsides, such as the sociological problems that came with the era beginning with Columbus. One cannot guess what Greenpeace and other environmental advocacy groups might do, but there are no native populations, not even whales, as permanent residents in the middle of the ocean [14].
Yes, if the Blue Revolution shows any kind of movement there is no doubt that society will prob-ably feel compelled to invoke another Law of the Sea marathon, this next one to adjudicate over who can use the open ocean. But one could say that that is the way human systems progress.
THE BLUE REVOLUTION AND HYDROGEN
As it is currently difficult to economically trans-port electricity thousand of miles across the ocean, hydrogen becomes an obvious medium. Current development trends featuring fuel cells and cleaner air make the combination of OTEC and hydrogen a natural choice, for hydrogen can quite conveniently be produced on floating platforms and shipped us-ing retrofitted tankers in the first stage, but with specially designed container ships in the future. The Japan World Energy Network (WE-NET) has conducted the International Clean Energy Network Using Hydrogen Conversion Project for nearly a decade now, and has focused on transport-ing hydrogen by sea, initially from the lowest cost hydrogen soon to be made available from Canadian hydroelectric facilities. Other alternatives are also being studied.
Among the more innovative marine hydrogen re-lated programs being explored are the following:
1. Large OTEC plantships someday will have hy-drogen as a product. Studies are available detail-ing the production of hydrogen via water electroly-sis on 50-400 MW OTEC plantships at costs low
enough to manufacture on board and delivered to land-based users of ammonia and fertilizers to compete with conventional options [13]. A 64 MW plantship could produce 8270 tons (7500 tonnes) of hydrogen (one million GJ net heating value) per year. When 1000 megawatt OTEC plantships be-come competitive, this option will bebe-come viable to directly convert seawater into hydrogen.
2. Marine biotechnology experiments have begun to combine a genetically engineered marine micro-organism, sunlight, and nutrients in the upwelled photic zone for the production of hydrogen. This remains a very long-term endeavor, as there will be many questions related to effects on the environ-ment, capturing of the hydrogen and economics of the process.
3. A floating plantship can process 10 tons of coal per day (1.24 kg/sec) to produce 47,400 tons (43,000 tonnes) of methanol annually, and because of the hydrogen from OTEC electrolysis, provide a 1:1.3 ratio of coal to methanol, whereas, typical plants today have a 1:0.6 ratio. There would also be the carbon sequestration benefit as mentioned earlier. Another variation, a renewable one, would use ma-rine biomass as the feedstock to replace coal, for a large portion of the overall coal cost is due just to delivery [15]. In either case, methanol might well be the ideal input fuel for reformers.
4. Methane hydrates in ocean seafloor sediments represent an enormous energy resource. The amount of CH4 gas trapped in these ice-like solids
is not known presently, but current estimates range between 1015 and 1016 standard m3 of gas.
Even at the lower end of this range, there is more energy in ocean floor methane hydrates than in all known reserves of conventional fossil fuels. Recov-ery of the CH4 for energy is problematic, however,
since the hydrates exist at depths in excess of 400 m and are generally found widely dispersed in se-diments with complex flow characteristics. Indus-trial scale production of fuel gas from hydrates will probably not be realized for the better part of a
generation. Exploitation of marine methane hy-drates (and ocean floor CH4 seeps) for specialized
subsea power application, on the other hand, may become reality within 5-10 years. The U.S. Navy has shown considerable interest in exploiting the in situ resource. Concepts being pursued include low-power, long-life biological fuel cells for seafloor moored instruments; methane/H2 fuel cells for
au-tonomous underwater vehicles and other submer-sibles; and H2 production (from hydrates) and
sto-rage on the seafloor to refuel these submersibles.
IN CONCLUSION
The pathway from the obvious availability of ocean temperature differential resources to com-mercially viable renewable hydrogen will involve decades of effort. Getting there from here can only be attained through a long-term and purposeful program which can yield early benefits while main-taining the ultimate vision. As Sputnik was the catalyst and Apollo the culmination capturing the spirit of the 20th Century, can a terrestrial
equiva-lent provide the galvanizing force in this new mil-lennium to take our society to the next level of hu-man development through intelligent utilization of our ocean resources in harmony with the natural environment? The Blue Revolution is poised to ac-complish this task, and hydrogen could well be the ideal energy form for this and all future millennia.
APPENDIX: ABOUT THE CO-AUTHORS
Patrick Takahashi retired as Professor of Engi-neering and Director of the Hawaii Natural Energy Institute at the University of Hawaii. In 1979, while working in the U.S. Congress, he assisted in drafting both the original OTEC and hydrogen bills that were eventually enacted into law, which for two decades now, have guided R&D in the United States for the former and a dozen years for the lat-ter. He was instrumental in working with others to bring to the University of Hawaii a number of na-tional centers, including the Nana-tional Science Foundation Marine Bioproducts Engineering
Cen-ter, Department of Interior Center for Marine Re-sources and Environmental Technology and De-partment of Energy Hydrogen Center of Excellence. He helped create the Pacific International Center for High Technology Research, and formed their OTEC engineering office, while providing funds to initiate the biohydrogen program at the University of Hawaii. He was awarded the Bechtel Energy Award by the American Society of Civil Engineers, and has produced for the United Nations a text-book on OTEC, a chapter in a solar energy publica-tion and various papers on sustainable resources. Stephen Masutani has been with the University of Hawaii and the Hawaii Natural Energy Institute (HNEI) since 1994. He is currently an Associate Researcher and director of HNEI’s Ocean Re-sources and Applications Laboratory. He also served with the Pacific International Center for High Technology Research from 1989 to 1998 as Senior Mechanical Engineer/CO2 Project Manager
and Program Manager. After receiving his M.S. and Ph.D. degrees from the High Temperature Gasdynamics Laboratory of Stanford University, he was a Visiting Scientist at the Hitachi Research Laboratory of Hitachi, Ltd. in Japan from 1985 to 1989. His current areas of research interest in-clude methane hydrates, CO2 ocean sequestration,
and marine environment technologies.
Kenji Sumida is past president of the East-West Center. He has served in a wide range of capacities, from vice-president at the University of Hawaii to general in the Air Force to co-founder of a computer service company. He was a vice-president for the Pacific International Center for High Technology Research, providing fiscal and administrative su-pervision over the OTEC project funded by the U.S. Department of Energy and Japan’s Ministry of Foreign Affairs. He has been associated with the Blue Revolution movement since the very early days of planning, and for several years, served on the Board of the Pacific Congress on Marine Science and Technology, International.
REFERENCES
1. P. Takahashi, U.S. Ocean Resources 2000: Planning for Development and Management, National Science Foundation and National Oceanic and Atmospheric Administration, June 9-11, 1992
2. D. Inouye, “The American Blue Revolution: a Solu-tion for the 21st Century,” Sea Technology, Vol. 33,
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Summit, for the Hawaii State Legislature, Honolulu, Hawaii, December 3-5, 1998
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